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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)
           9  TCP/IP Network Management Framework and Protocols (SNMP and RMON)
                9  TCP/IP Structure of Management Information (SMI) and Management Information Bases (MIBs)

Previous Topic/Section
TCP/IP MIB Objects, Object Characteristics and Object Types
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TCP/IP MIB Modules and Object Groups
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TCP/IP MIB Object Descriptors and Identifiers and the Object Name Hierarchy and Name Notation
(Page 2 of 4)

The MIB Object Name Hierarchy

Text names are convenient, but they are generally unstructured. There are at present over 10,000 different MIB objects, and even if each has a distinct text name, a huge collection of such names doesn't help us to manage these objects and see how they are related. For this, we need a more structured approach to categorizing and naming objects.

This problem is similar to another problem that you may recall reading about: the problem of how to assign names on the Internet. Originally names for hosts were simple, “flat” names, but this quickly grew unwieldy. The Domain Name System (DNS) formalized a structured hierarchy for domain names. The DNS hierarchical name space allows every device to be arranged into a single hierarchical tree structure. The name of the device can be formed by traversing the tree from the top down to the location of the device, listing the labels traversed separated by dots. For example, the Web server of The PC Guide is at “www.pcguide.com”.

This exact same concept is used to organize MIB objects in SNMP. A single universal hierarchy is used that contains all MIB objects. It is hierarchical in nature, and split into levels from the most general to the most specific. Each object has a particular place in the hierarchy. The names are formed by following the labels from the top of the tree down to the place where the object is located, and separating them with “dots”. (SNMP doesn't reverse the order of the labels the way DNS does, however. They are listed top-down from left to right.)

There is another important difference between the MIB name hierarchy and the DNS one: the MIB name hierarchy is even more universal than the one for DNS. The entire subtree of all MIB objects is just one branch of the full, international object hierarchy maintained by ISO and ITU. This object identification hierarchy is so general that it can contain a name for every object or variable in use by any technology in the entire world. And possibly other planets. Or solar systems. J

The reason for my jocularity will become apparent in a moment. Suffice to say, this object tree is enormous. Each node in this tree is identified with both a label and an integer. The labels are for descriptive purposes; object (or subtree) identifiers are formed by listing the numbers in sequence from the top of the tree down to the node, separated by dots. (The text labels can be used for names too but are not because they would get very long due to how deep the tree structure is.)

Key Concept: SNMP MIB objects have two names. The first is a text object descriptor, which provides a means of addressing the object in a way that is familiar and easy for humans. The second is the object identifier, which consists of a sequence of integers that specifies the location of the object in the global object hierarchy maintained by the international standards bodies ISO and ITU.



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TCP/IP MIB Objects, Object Characteristics and Object Types
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TCP/IP MIB Modules and Object Groups
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Version 3.0 - Version Date: September 20, 2005

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